High speed gear with oil lubrication, especially for environmentally sealed railway driving mechanism

ABSTRACT

The invention relates to a high-speed gear with oil lubrication, with oil-recycling ducts ( 8 ) leading out of the labyrinth chambers of contactless shaft seals ( 6 ) to the crankcase ( 5 ) of the gear casing ( 3 ). According to the invention, the oil-recycling ducts ( 8 ) terminate in regions ( 10 ) in which a vacuum is automatically established during running operation, independently of the direction of rotation of the gear.

BACKGROUND OF THE INVENTION

The invention relates to a high-speed gear with oil lubrication,especially for environmentally-sealed railway driving mechanisms, withoil-recycling ducts leading out of the labyrinth chambers of contactlessshaft seals to the crankcase of the gear casing.

In the lubrication of modern, high-speed railway driving mechanisms,generally the teeth of the large wheel take up oil from the crankcase ofthe gear casing in the manner of splash lubrication during the startupprocess; the driving pinion is wetted and, due to its fracturedstructure, a fine oil-air mixture is formed as the rpm increases. Thismixture is distributed in the entire gear, and thus also lubricates thebearings of the drive shafts in the gear casing.

Assuring a reliable, no-wear and extensively oil- and gas-tight sealtoward the outside at the contactless shaft seals of these bearingsposes a major problem for drives with high-speed, large gears. Usually,labyrinth seals whose function lies in throttling the pressure in thegap are used. The oil mist that condenses in the labyrinth chambers ofthe seals is continuously removed via a siphon system, and re-circulatedinto the closed gear casing, which is intended to prevent a significantamount of leaked oil from exiting via the external dirt-removal chambersof the labyrinth seals. The oil-recycling conduits are sloped for thispurpose, and terminate above the crankcase.

In very high-speed gears, it appears that the oil-air mixture is carriedalong, as a so-called drag current, at virtually the same angular speedas the large wheel in the gear casing, and is warmed considerably due toinherent friction, thereby expanding. Consequently, it has a morepronounced effect on the labyrinth seals. This requires, among otherthings, highly-reliable oil recycling from the labyrinth chambers of theseals to prevent the escape of oil.

To reduce the frictional heat of the oil mist to a tolerable level, itis necessary to keep the quantity of oil in the gear casing as small aspossible, and thus keep the viscosity of the oil-air mixture as low aspossible, and to create the smoothest possible flow conditions in thegear casing. It must also be ensured, however, that the gear absolutelynot be allowed to run dry, which would lead to jamming; therefore, it isimperative that a quantity of oil required for reliable operation bemaintained at all times. Hence, the oil-supply tolerances are verytight, and must be monitored diligently.

Particularly for railway driving mechanisms, but also for otherapplicable, high-speed gears, it is an object to improve the manner inwhich oil is conveyed out of the gap seals in order to prevent leakedoil to the greatest possible extent, and to create a highly-reliable,that is, sensitive and position-tolerant, oil-supply display, withoutsignificantly disturbing the flow conditions in the gear casing.

SUMMARY OF THE INVENTION

According to the invention, this object generally is accomplished by ahigh-speed gear arrangement with oil lubrication, especially forenvironmentally-sealed railway driving mechanisms, with oil-recyclingducts leading out of the labyrinth chambers of contactless shaft sealsto the crankcase of the gear casing or gear box, and wherein the ends ofthe oil-recycling ducts leading to the crankcase terminate in regions inwhich a relative vacuum is automatically established during runningoperation, independently of the direction of rotation of the geararrangement, with the regions with a vacuum being formed by axial narrowpoints or constrictions between the tooth region of the large wheel ofthe gear arrangement and the bordering walls of the gear casing.Advantageous embodiments likewise are disclosed.

According to the invention, the Bernoulli effect is utilized during gearoperation to generate a vacuum at the termination point of theoil-recycling ducts, which effectively supports the flow of oil from thelabyrinth chambers of contactless shaft seals. According to Bernoulli,the static pressure in a fast-moving fluid is lower than in a non-movingor slower fluid; specifically, the larger the flow difference, the lowerthe static pressure. If the region of the gear casing through which thedrag current passes is artificially narrowed, the speed of the dragcurrent increases in this region, and the static pressure drops at thislocation relative to the entire system. If the oil-recycling ductsterminate in such a region, an eddy is formed in the oil-recycling ductsduring operation, which essentially supports the flow-off of the coilthat has condensed in the seal system.

The discussed arrangement has the same physical effect as a venturinozzle, although it is specified for a different purpose. The narrowpoint is advantageously created in a region of the gear casing in whichthe highest speed of the drag current dominates, namely near theperiphery of the large wheel. A particularly well-suited location isdirectly above the crankcase, utilizing the guide incline of theoil-recycling ducts. If the constricted areas are formed by materialbuildups in the walls of the gear casing in this region, these areas canadvantageously also accommodate bores for the oil-recycling ducts fromthe large-wheel bearing. The material buildups are preferably embodiedsuch that the change in the cross section of the drag current iseffected in both directions of rotation with the least possible eddyformation. Furthermore, a float, which is visible through a viewingglass provided for checking the oil supply, can be seated in adirectly-adjacent bore. With this arrangement of the float in thebuilt-up region of the housing wall, the flow behavior of the oil-airmixture is not disturbed in either the narrow point or in furtherflow-sensitive regions; additionally, the complicated tubular guides forthe float that would otherwise be necessary can be omitted. Moreover,the oil level is read in this region if, in an advantageous embodimentof the invention, it coincides with the center of gravity of the surfaceof the permissible oil-bath level, independently of the inclination ofthe gear casing, as stipulated by, for example, the inclination of theextension. The oil-recycling ducts terminating here ensure that asufficient quantity of oil is available for the float when the gear isinoperative.

For additionally utilizing the eddy effect to convey the oil out of thebearing of the drive pinion, the oil-recycling lines of the pinion canlikewise terminate in the artificially-narrowed region.

The embodiment of the gear according to the invention has a very lowcost and space requirement, and production is non-problematic. Thedevice itself is maintenance-free and requires no external power. Withthe exception of the float, which may or may not be used to raise thereading level, no mechanically-moved parts are required. Furtheradvantageous embodiments ensue from the dependent claims.

The invention is described below by way of an exemplary embodiment.

FIG. 1 shows a section I—I through the gear casing of a railway drivingmechanism, in the plane of the large-wheel axle according to FIG. 3.

FIG. 2 shows a section II—II according to FIG. 3, parallel to sectionI—I, in the plane of the center of gravity of the oil level.

FIG. 3 is a side view of the gear casing in the direction of the axlebody.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2, 1 represents the large wheel of a railway drivingmechanism, which is driven by a pinion, not shown in detail. The largewheel 1 is screwed to a large-wheel body 2, which is shrunken onto anaxle shaft of a rail car, not shown in detail. The large wheel 1 and thedriving pinion are seated on cylindrical roller bearings in a gearcasing 3. The gear casing 3 ends at the bottom with a crankcase 5, whichis filled with gear oil up to about the center of the teeth of the largewheel 1. Labyrinth seals 6 create the seal between the gear casing 3 andthe large-wheel body 2. These contactless gap seals permit high relativespeeds, and are wear-free in principle. It is not possible, however, tocompletely avoid leakage of the labyrinth seals 6 due to the oil-mistpressure that is established in high-speed operation, so leaked oil isfiltered out by way of a siphon system 7 and returned nearly in itsentirety to the crankcase 5 through oil-recycling ducts 8. only verysmall traces of oil that are no longer circulated are conveyed away,with dirt particles that have deposited externally, by way of theexternal dirt-removal chambers 9.

The contour of the gear casing 3, which is indicated in a dashed line inFIGS. 1 and 2, is optimal in terms of flow. This contour permits thedrag current, comprising an oil-air mixture, to be carried along withoutfriction or eddy currents, so the oil mist is not warmed excessively. Inthe region of the lowermost teeth and the tooth base of the large wheel1, however, the contours of the side walls of the gear casing 3 areembodied such that narrowed regions 10 are formed. For this purpose, thehousing wall is continuously thickened such that the inside walls of thegear casing 3 extend perpendicular to below the crankcase 5 in theregion of the curve maximum of the material buildups, resulting in thedesired narrowed points, narrowings or constrictions in the lower regionof the gear rim and the tooth base of the large wheel 1.

An oil-recycling duct 8 of the large wheel 1 is embodied by a transversebore 8 a extending to the siphon system, and an adjoining, vertical bore8 b, the bores being cut into the material buildup of the housing walls.The vertical bore 8 b terminates at the height of the lower tooth regionof the large wheel 1, inside the curve maximum of the material buildup,that is, exactly in the region 10, in which the largest relativevacuum—in comparison to the entire system—is established within theclosed gear casing 3 while the gear is running. This vacuum creates aneddy, which supports the flow of leaked oil out of the labyrinthchambers of the seals 6 or the siphon systems 7. Because of the suction,virtually no more gear oil escapes, which is environmentally friendlyand assures a constant quantity of oil in the gear casing 3 for alengthy period of time.

The latter point is particularly crucial for the service life of thegear, because in high-speed gears, the smallest-possible quantity of oilmust be used to keep the viscosity of the forming oil-air mixture, andthus its warming tendency, as low as possible, without the gear beingdestroyed by a lack of oil. A precise control of the oil level withoutinterfering influences of the flow conditions is therefore a furtherconstraint for high-speed driving mechanisms.

FIGS. 2 and 3 illustrate a relevant embodiment. According to thesedepictions, a vertical float bore 11 is provided directly in front of orbehind the curve summit of the material buildup in a wall of the gearcasing 3; this bore is connected at the bottom to the crankcase 5, andis crossed at the top by a horizontal recess 12, which is sealed towardthe outside by a viewing glass 13. The float 14 assists in raising theobservation height above the separating seam between the gear casing 3and the crankcase 5, which approximately coincides with the oil level,without necessitating additional parts that would make the display morecostly, or would have a favorable effect on other interfering influencesin the flow-sensitive region of the gear interior.

As can be seen from FIG. 3, in an advantageous modification of theinvention, the center of gravity of the surface of the oil levelcoincides exactly with the location of the oil-supply display, whichallows the oil supply to be recognized completely independently ofwhatever tilted position the gear casing 3 may assume.

It can also be seen clearly from FIG. 3 that the oil-recycling ducts 15are guided from the pinion bearing 16 into the narrow-flow region 10below the large-wheel bearing 17, so the oil is also suctioned away fromthe pinion bearing 16 with the use of the Bernoulli effect.

What is claimed is:
 1. A high-speed gear arrangement with oillubrication for environmentally-sealed railway driving mechanisms,including a gear casing with oil-recycling ducts leading out oflabyrinth chambers of contactless shaft seals to a crankcase of the gearcasing, and wherein the oil-recycling ducts terminate in regions inwhich a relative vacuum is automatically established during runningoperation, independently of the direction of rotation of the geararrangement, with the regions with a vacuum being formed by axial narrowpoints between a tooth region of a large wheel of the gear arrangementand bordering walls of the gear casing.
 2. The high-speed geararrangement according to claim 1, wherein the narrow points are formedby material buildups in the bordering walls of the gear casing.
 3. Thehigh-speed gear arrangement according to claim 2, wherein the materialbuildups are formed such that a drag current only has small eddycurrents in both directions.
 4. The high-speed gear arrangementaccording to claim 1, wherein the labyrinth chambers of the shaft sealsare connected to the oil-recycling ducts by a siphon system.
 5. Thehigh-speed gear arrangement according to claim 2, wherein theoil-recycling ducts from a bearing for the large-wheel are formed bybores in the material buildups.
 6. The high-speed gear arrangementaccording to claim 2, wherein the oil-recycling ducts from a bearing fora pinion of the gearing arrangement are formed by oil-recycling linesthat are formed into the walls of the gear casing.
 7. An oil-supplydisplay for a high-speed gear arrangement according to claim 3, whereina bore that communicates with the crankcase is provided for a float nearthe peak of a material buildup, with the float being visible through aviewing glass.
 8. The oil-supply display according to claim 7, whereinthe bore lies in a center of gravity of the surface of the permissibleoil-bath level.